Since cubic boron nitride (which may be hereinafter referred to as “cBN”) is the highest hardness substance next to a diamond, it is used for various kinds of cutting tools and the like. Such cBN is generally used as a composite sintered material together with a binder, rather than used alone.
Recently, a work material and cutting conditions have been diversified in terms of applications to a cutting tool, which leads to a high level of demands made for a cutting tool using cBN. Particularly, it is desired to improve wear resistance and fracture resistance.
For example, Japanese Patent Laying-Open No. 2007-144615 (PTD 1) discloses a cBN cutting tool insert that is excellent in resistance to chipping and cutting edge breakage, and also discloses that the composition of a binder included in this insert exhibits a wide composition range of TiC1-xNx. WO2010/119962 (PTD 2) discloses a composite sintered material that allows the fracture resistance and the toughness to be improved without reducing the wear resistance, and also discloses that the binder included in the composite sintered material contains titanium nitride and titanium carbonitride.